Elucidating the effects of electron beam irradiation on cellulose and lignin and the consequences for wood-based biorefineries

SUPERVISOR: Antje POTTHAST

PROJECT ASSIGNED TO: Oliver SAROSI

Aside from thermal utilization and construction, wood is a suitable composite material for complete chemical valorization by the means of a fully integrated wood biorefinery. The ubiquity of wood makes cellulose the most abundant polymer originating from renewable resources. Cellulosic fibers from wood find their major application in the textile industry with a market volume of over $772 billion [1]. Wood pulping - the process for cellulose extraction from wood – is performed at high temperatures, caustic soda or sulfuric acid concentrations and necessitate extensive chemical bleaching. This thesis aims at the industrial utilization of alternative, more efficient bleaching methods to partly replace or supplement conventional bleaching stages in the production of dissolving pulp. The industry partners for this project are the WoodKPlus Ltd. and the Lenzing Inc., Upper Austria. A moderate reduction of the degree of polymerization of cellulose is a pre-requisite for a good processability of the pulp during the viscose and lyocell process. This is usually done by ozone or hypochlorite treatments. As an alternative, endoglucanases (EG) (EC 3.2.1.4) catalyze the internal cleavage of the cellulose chain. The enzymes originate mainly from saprotrophic fungi growing on wood. Aside from their natural origin, EGs provide additional process benefits like lower chemical input, lower temperatures (thermal input), facilitated waste treatment and improved product properties. The difficulty in the industrial utilization of EGs lies in their controlled application to achieve a strictly defined reduction of the degree of polymerization. This is mainly owed to the complexity of the lignocellulosic substrate and the interaction of its components with the enzyme.

 ^{Figure 1: X-ray 3D-crystalstructure of the catalytic domain of the endo-1,4-β-glucanase from Trichoderma reesei (EG1) with highlighted catalytic center. Adapted from Kleywegt et al. and visualized in PyMOL [2].} [1]    "India world's second largest textiles exporter: UN Comtrade". Economic Times. June 2, 2014.
[2]    Kleywegt, G.J., et al., The crystal structure of the catalytic core domain of endoglucanase I from Trichoderma reesei at 3.6 Å resolution, and a comparison with related enzymes11Edited by K.Nagai. Journal of Molecular Biology, 1997. 272(3): p. 383-397.